This would suggest that at one time the universe was compacted.(a.i.2)The second big idea seen to support the Big Bang theory was the discovery of Cosmic Microwave Background (CMB) radiation. (a.i.2.a)In 1948, three scientists Gamow, Alpher, and Herman predicted that based on the idea that the universe started out hot and dense, and proceeded to expand and cool, that there should be some kind of relic radiation left over spread out throughout the universe.(a.i.2.b)In 1965, two radio astronomers, Penzias and Wilson, discovered what is cited today as one of the most compelling pieces of evidence of the Big Bang--microwave radiation with a temperature of about 2.7K that uniformly pervades the entire observable universe. (a.i.2.c)This radiation, known as CMB radiation, is interpreted to be the left over heat from the Big Bang.(a.i.3)The third idea used to support the Big Bang theory is the idea of Big Bang Nucleosynthesis, which suggests that the universe should mainly consist of light elements such as helium. (a.i.3.a)The idea of Big Bang Nucleosynthesis is that within the first few minutes of the Big Bang, temperatures and densities were high enough that protons and neutrons floated as free particles--not bound up in atoms. (a.i.3.b)For the first fifteen minutes or so, these particles underwent nuclear fusion, forming light elements such as helium and hydrogen (a specific type of hydrogen called deuterium).
(a.i.3.c)The idea is that there were only a few minutes for these reactions to occur because the universe was expanding rapidly--temperature and density were dropping. So, there was no opportunity for heavier elements to form.(a.i.3.d)Therefore, the universe should consist almost entirely of light elements. Investigation shows that indeed, the older an object is in space, the less heavy elements it contains, but even really old objects contain at least 25% helium.(a.i.3.e)The gist is, the abundance of light elements such as Helium (almost 25% of matter in the universe) and Hydrogen (about 3/4 of all matter) is seen as one of the big three pieces of evidence to support the Big Bang theory161)The gravitational attraction of the moon and sun, acting on the Earth, has two consequences that arise because the Earth is not a perfect Sphere but rather an ablate spheroid. (a.i.1.a)Since the Earth is not exactly spherical, its curvature varies with location.162)The shape of the Earth and the Gravitational pull of the moon and the sun cause two phenomena: a.i) Tides and precession. a.ii)The differential gravitational forces of the moon's attraction on different parts of the Earth with respect to its center are called tidal forces. (a.ii.1.a)The areas of the Earth facing the moon have a higher gravitational pull than those away from the moon. This pull causes the Earth to slightly distort, rising up and down and tilting as a fluid surface, causing the sea level changes.
- Winter '12